Study participants were asked about their sexual characteristics and their partners’ characteristics. Among those whose partners’ activities were labeled as high risk, 53% were diagnosed with an STD. Among those whose own behavior was labeled as high risk, 38% were diagnosed with an STD.

The riskiest characteristics were age difference and if the partner had had an STD in the past year.

“If you are choosing high-risk partners, you are much more likely to have an STD, even when we account for your condom-use patterns,” Stephanie A.S. Staras, lead author and an assistant professor of epidemiology and health policy research in the University of Florida College of Medicine, says in a written statement.

“The theory is simple: You need to have sex with someone who has an STD to get an STD. Based on the prevalence of STDs in the United States, it seems like the public may not fully understand their risk.”